of  the  Arsines.  - 


i 


M 


I 


t 


- ( 


By  William  M,  Dehn.  . 


I 


\ 


-i 


4 


,^’;4 


19345 


Reprinted  from  the  American  Chemical  Journal.  Vol.  XI,.  No.  i. 
July,  1908.] 


[Contributions  from  the  Chemical  Laboratory  of  the  University  of  Illinois.] 


REACTIONS  OF  THE  ARSINES. 

By  William  M.  Dehn. 

In  an  earlier  contribution^  it  was  held  that  the  reactions 
of  the  arsines  and  their  derivatives  can  be  divided  into  two 
general  classes,  viz.,  those  that  involve 

(1)  Addition. 

(2)  Addition  and  subsequent  dissociation;  in  other  words, 
these  reactions  result  from  alternate  changes  of 

(1)  Trivalent  arsenic  to  pentavalent  arsenic,  and 

(2)  Pentavalent  arsenic  to  trivalent  arsenic. 

The  oscillations  of  the  arsenic  valencies  are  best  illustrated 
b}'”  the  following  reactions: 


I. 


11. 


III. 


IV. 


(a) 

AsXg 

AsXg 

RASX2 

RAsX^ 

R2ASX 

R2ASX 

RgAS 

RgAS 


Halogen- Alkyl  Series  (A). 

(b) 


RX 

RX 

RX 

RX 

RX 

RX 

RX 

RX 


<— 


(c) 

RASX2 

+ 

X/ 

RAsXg 

+ 

X^" 

RgAsX 

+ 

X,' 

RgAsX 

+ 

X/ 

RgAS 

+ 

RgAS 

+ 

X,'’ 

1 This  Journal,  36,  5. 

2 See  page  121. 

^ Evident  in  the  presence  of  sodium. 
^ Ann.  Chem.  (Liebig),  107,  274. 

5 Ibid.,  107,  274. 

® See  page  107. 

^ Evident  in  the  presence  of  sodium. 
8 Ann.  Chem.  (Liebig),  107,  266. 


RAsX,2  - 

RAsX^s  ■ 

RgAsXg®  - 

R2AsX3»  - 
R3ASX2'®  - 
R3ASX2''  - 
R4AsX'^ 

R^AsX'-^ 

^ Ibid.,  107,  269. 

Probable. 

Evident  in  the  presence  of  sodium. 

12  Ann.  Chem.  (Liebig),  89,  330;  112,  231. 

13  Ibid.,  89,  330. 

I'l  Ibid.,  112,  230.  Compt.  rend.,  39,  541 ; 

49,  87.  This  Journal.,  33,  115. 

13  Ann.  Chem.  (Liebig),  89,  311. 


Reactions  of  the  Arsines. 


89 


It  will  be  observed  that  columns  (a)  and  (c)  involve  tri- 
valent  arsenic,  and  column  (6)  pentavalent  arsenic.  Now, 
since  it  can  be  demonstrated  that  the  compounds  given  are 
really  formed  in  the  order  indicated,  it  is  concluded  that 
continuous  progress  through  reactions  I.  to  IV.  involves  a 
regular  alternation  of  tri~  and  pentavalent  arsenic. 

This  operation  of  a variable  valency  is  further  illustrated 
by  the  following 

Hydrogen-Halogen-Alkyl  Series  (B).^ 

(a)  (b)  (c) 

I.  AsHj  + RX  RASH3X2  RASH2  + HX^ 

II.  AsHg  + RX  ->  RAsHgX  ->  RAsHX  + 

III.  RAsH^  + RX  — ^ R^AsH^X®  <-  R^AsH  + HX« 

IV.  RAsH^  + RX  — > R^AsH^X  R^AsX  + 

V.  RAsHX  + RX  ->  R^AsHXa*  R2ASH  + X2« 

VI.  RAsHX  + RX  ->  R2ASHX2  — R2ASX  + HX'o 

VII.  R2ASH  + RX  ->  RgAsHX^  ->  R3AS  + HX'2 

' RgAsHX  ^ RgAs  + HX'3 

VIII.  R2ASX  + RX  ->  R3ASX2''  ->  R3AS  + X2'« 

R2ASX  + RX  R3ASX2''  R3AS  + X2'’ 

IX.  R3AS  + RX  ->  R^AsX'® 

RgAs  + RX  ^ R4AsX'» 


From  the  fact  that  most  of  the  indicated  reactions  have  been 
studied,  and  that  their  courses  proceed  as  indicated  by  the 
arrows,  general  reversibility  of  reaction  is  very  improbable. 
Reactions  1(a)  and  1(c)  both  yield  the  same  product. 


H 

} 

X 


RH2As\  , which  decomposes  as  indicated  in  11(6).  Reac- 


tions  III  (a)  and  III(c)  yield  the  compound  R2HAs< 


.H 

x’ 


^ It  may  be  observed  here  that  arsenic,  unlike  nitrogen,  has  a greater  affinity 
for  halogen  than  for  hydrogen,  and  also  for  alkyl  than  for  halogen  or  halogen  acid. 
2 Not  studied,  but  very  probable,  from  analogy  to  the  formation  of  primary 


arsine. 

3 Vide  This  Journal,  33,  126  ; see  pages  107  and  115. 


* Ibid. 

^ Vide  ibid.,  33,  128;  see  page  107. 
6 Vide  ibid.,  36,  22-24. 

T Ibid. 

® Not  studied. 

® This  Journal,  36,  14-18. 

10  Ibid. 


12  Ibid. 

13  Not  studied,  but  very  probable. 

1^  This  Journal,  36,  1. 

15  Ann.  Chem.  (Liebig),  112,  228. 

10  Evident  in  the  presence  of  sodium. 
11^  Ann.  Chem.  (Liebig),  112,  228. 

18  Ibid. 


11 /6id.,36,  18-19;seepages  121,  122and  123.  i*  89,  321.  Also  cf.  page  112. 


90 


Dehn. 


and  this  decomposes  as  shown  in  IV(6).  Reaction  V(c)  and 

probably  V(a)  yield  the  product  R2HAs<f  , which  decom- 

poses  as  indicated  in  VI (6).  Reactions  VII (a)  and  VII (c) 

/H 

yield  the  compound  RgAs^^  , which  decomposes  as  repre- 
sented in  VII (6).  Reactions  VIII (a)  and  VIII (c)  yield  the 
product  RgAs^  , which  probably  reversibly  decomposes  as 
indicated  in  Vlll(a).  Reaction  IX(a)  yields  the  compound 

A 

RgAs^  , which  decomposes  as  indicated  in  IX  (6). 

^X 

Now,  since  reactions  1(a),  Ill(a),  Vll(a),  and  Vlll(a), 
as  well  as  IX (a),  all  yield  the  compound  R4ASX  in  the  pres- 
ence of  an  excess  of  alkyl  halide,  it  is  concluded  that  the  arson- 
ium  compound  is  formed  by  a series  of  intermediate  reactions 
involving  molecular  compounds  which  immediately  or  slowly 
dissociate,  and  that  the  process  is  repeated  until  the  stable  end 
products  are  formed} 

As  the  result  of  a number  of  years  of  observation  and  study 
of  the  reactions  of  arsenic,  the  conviction  has  grown  that  the 
activity  of  this  element  cannot  always  be  explained  on  the 
basis  either  of  ionic  or  of  kinetic-molecular  mechanics.  Briefly 
considered,  this  conviction  has  resulted  from  observation  of 
the  facts  (i)  that  most  of  the  arsenic  reactions  are  nonelectro- 
lytic  or,  in  other  words,  they  take  place  in  the  absence  of  water 
and  (2)  that,  between  the  starting  compounds  and  the  most 
easily  separated  end  product,  there  are  observed  other  and 


1 Analogous  alternations  of  valency  and  formation  of  intermediate  compounds 
are  recognized  in  the  reactions  of  the  amine,  phosphine,  and  stibine  derivatives,  as, 
for  instance:  (1)  in  the  Hoffmann  series  of  reactions,  when  alkyl  iodides  and  am- 
monia are  heated  together  and  form  a mixture  of  the  four  classes  of  amines;  (2)  when 
alkyl  iodides  are  heated  with  phosphonium  iodide  in  the  presence  of  zinc  oxide  and 
form  a mixture  of  primary  and  secondary  phosphines;  and  (3)  when  alkyl  iodides 
are  treated  with  sodium  antimonides  and  form  tertiary  and  quaternary  stibines. 
Ease  of  dissociation  of  the  various  molecular  compounds  determines  the  yields  of  the 
respective  derivatives ; in  general,  with  the  element  nitrogen  primary  amines  are  formed 
in  greater  quantity;  with  phosphorus,  primary  and  secondary  phosphines;  and  with 
arsenic  and  antimony,  the  respective  quaternary  compounds  are  obtained  in  greater 
quantity. 


Reactions  of  the  Arsines. 


91 


usually  crystalline  products,  which  often  can  be  separated  and 
analyzed.  Mention  of  these  intermediate  products  has  been 
made  in  previous  contributions;^  a systematic  study  is  made 
herein  to  establish  their  frequent  formation  and  to  secure 
evidence  leading  to  the  general  conclusion  that  compounds 
of  the  element  arsenic  react  largely  by  initial  coalescence  with 
the  reagent. 

Whereas  the  nitrogen-organic  and  the  oxygen-organic 
compounds  yield  intermediate  products,  their  unstable  proper- 
ties and  usually  liquid  condition  prevent  their  easy  and  sys- 
tematic study.  The  arsenic-organic  compounds,  on  the  other 
hand,  containing  the  heavy  element  arsenic,  usually  form 
crystalline  intermediate  products  which  can  often  be  separa- 
ted and  analyzed  and  therefore  the  arsenic  derivatives  offer  a 
productive  field  for  the  study  of  chemical  statics  and  dynamics. 

Let  us  consider  first,  by  way  of  illustration,  the  spontaneous 
oxidation  of  methylarsine  by  means  of  atmospheric  oxygen : 

CH3ASH2  + 02  = CH3ASO  + H2O, 

2CH3ASH2  + 3O2  = 2CH3AsO(OH)2. 

The  first  reaction  is  instantaneous,  but  the  second  is  in- 
complete even  after  two  weeks. 

If  applied  here,  Engler’s  theory  of  autoxidation^  should 

/O 

involve  an  initial  addition  of  a molecule  of  oxygen:  RH2As<*^  |. 

This  “moloxide,”  by  elimination  of  water,  gives  the  end 
products,  water  and  methylarsine  oxide,  RAs  = 0.  It  is 
not  impossible,  however,  that  the  above  peroxide  form  suffers 

.OH 

a molecular  rearrangement  into  the  compound  RAs<^ 

^OH 

before  splitting  off  water;  confirmation  of  the  probable  forma- 
tion of  an  addition  product  of  the  arsine  and  oxygen  was  de- 
duced (i)  from  the  observed  absence  of  condensed  vapors  of 
water,  proportional  to  the  theoretical  quantity,  and  (2)  from 
the  slow  formation  of  methylarsonic  acid,  which,  in  accord- 

^ See  This  Journal,  33,  101;  35,  1.  J.  Am.  Chem.  Soc.,  28,  347. 

^ C.  Engler  und  J.  Weissberg:  Kritische  Studien  tiber  die  Vorgange  der  Autoxy- 
dation  (1904),  63. 


92 


Dehn. 


ance  with  Engler’s  theory,  could  be  formed  in  the  manner 
indicated  below: 


(HO^RAs 

'v 

'O- 


AsR(OH)2. 

-q/ 


The  analogous  autoxidations  of  secondary  arsines^  are 
easily  accounted  for  in  the  same  manner: 

R,As  — H 


R,HAs/ 

* S. 


/O 


R,As; 


''O 


O— H 
O 


or 


0 

1 - 

O 

R,  As  — H 


RjAsv 


>0  4-  H^O, 
R,As/ 


the  addition  of  one  molecule  of  oxygen  to  one  molecule  or  to 
two  molecules  of  the  arsine  determining  whether  cacodylic 
acid  or  cacodylic  oxide  is  formed. ^ 

The  molecular  rearrangement  of  the  above-mentioned 
/O  yO 

compounds,  RHjAs/  \ and  R2HAs<  j , to  form  the  compoimds 
.OH  .OH 

R — As<Q  and  R2As:^  , necessitates  a shifting  of  the  hy- 
^OH  ^O 

drogen  atoms^  and  a rearrangement  of  the  oxygen  valencies,  un- 
less it  is  assumed  that  kinetic  or  ionic  dissociations  first  take 
place  as  indicated  below: 

H 


H 


R — As/ 


O 


^O 


H 


and  R — As 


R 


/ 


O 


o 


and  that  these  dissociated  parts  readjust  themselves. 

1 This  Journal,  35,  9. 

* Usually  the  two  compounds  are  formed  in  nearly  equal  quantities.  This  Jour- 
nal, 35,  14. 

3 Atomic  shifting,  an  assumption  not  new  in  chemical  statics  and  dynamics,  can- 
not, of  course,  be  dispensed  with  as  an  explanation  of  many  reactions,  particularly 
those  included  under  tautomeric  forms. 


Reactions  of  the  Arsines. 


93 


The  latter  hypothesis  is  unnecessary  and,  in  fact,  is  untena- 
ble because  it  assumes  an  effect  without  providing  a probable 
cause.  We  have  only  to  conceive  that  the  atoms  of  hydrogen, 
by  virtue  of  kinetic  motion  and  while  being  continuously 
held  within  the  spheres  of  attraction,^  pass  to  the  intersection 
of  the  spheres  of  oxygen  and  arsenic  attractions  (Fig.  I.), 
and  then  beyond  the  appreciable  attraction  of  arsenic  (Fig. 
II.).  In  this  manner  we  come  to  an  easy  understanding  of 
atomic  shifting  without  employing  any  new  theories  or  re- 
sorting to  other  than  the  fundamental  assumptions  of  the 
science. 


Fig.  I.  Fig.  II. 


That  molecular  coalescence  is  the  inevitable  preliminary  con- 
dition of  arsine  reactions  is  confirmed  by  the  behavior  of  di- 
methylarsine  with  nitric  acid.^  Normal  nitric  acid  (i  mol.) 
does  not  react  with  the  arsine  although  the  mixture  is  heated 
for  one  hour  at  125°;  concentrated  nitric  acid  (i  mol.)  reacts 
with  explosive  violence.  In  the  former  case,  the  nitric  acid 
is  ionized)  in  the  latter,  its  condition  is  molecular.  In  other 
words,  the  compound  H — O — NO2  has,  but  the  group  — O — NOj 
has  not,  the  property  of  adding  to  the  arsine  and  of  yielding 
the  end  product,  cacodylic  acid.  If  the  doubly  bound  oxygen 
atoms  of  the  nitrate  group  were  the  active  portion,  then  both 
ionic  and  molecular  nitric  acid  should  react;  however,  since 
only  molecular  nitric  acid  reacts,  only  the  H — O — N part  of 
the  acid  offers  hope  of  a satisfactory  explanation.  If  initial 
molecular  coalescence  is  the  indispensable  criterion,  then  the 
following  preliminary  mechanics  are  conceivable: 

1 Mechanical  arrangements  and  invariability  of  quantity  and  position  are,  of 
course,  improbable  conceptions  of  valency. 

2 This  Journal,  36,  27. 


94 


Dehn. 


R,As  — H 

II  R^As— H 

II  ^ hq/^no,  ’ 

H— O — NO, 

dimethylarsine  nitrate^  being  first  formed. 

Since  the  formation  of  the  analogous  arsine  salt, 

[(CH3),AsH]2.H,SO„ 

was  proven  in  the  case  of  sulphuric  acid,*  the  probable  forma- 

1 Objections  may  be  raised  as  to  the  structure  of  this  salt,  on  the  grounds  that 
it  is  not  strictly  analogous  to  the  structme  of  ammonium  nitrate,  H4N — O — NO2:  how- 
ever, there  is  no  evidence  that  these  salts  are  strictly  analogous.  The  fact  that  hy- 
droxyl attached  to  arsenic  constitutes  a more  stable  combination  than  hydrogen 
attached  to  arsenic,  the  reverse  being  true  in  the  case  of  nitrogen,  argues  a difference 
in  these  salts. 

Since,  in  the  case  of  ammonia  and  hydrochloric  acid,  at  least  a trace  of  water 
is  necessary  (Hughes;  Phil.  Mag.,  36,  53;  Baker;  J.  Chem.  Soc.,  65,  611)  to  form  am- 
monium chloride,  it  is  usually  held  that  ionized  hydrochloric  acid  adds  to  ammonia; 
of  course,  kinetic  dissociation  is  precluded  for  the  reason  that  hydrochloric  acid  does 
not  begin  to  dissociate  below  1000®  (Ber.  d.  chem.  Ges.,  6,  423).  However,  initial 
ionic  or  kinetic  dissociations  are  not  the  only  possible  explanations  of  these  phenomena ; 
the  water  that  is  necessary  may  add  in  the  following  manner; 

H 

I 

H3N=-  =0  — NH4OH ; 

H 

and  then  the  acid  and  base  may  react,  either  through  their  ions,  or  as  indicated  be- 
low; 

Cl 

I 

H4N  — 0=  =C1  — >-  H4N— O— H — H4N  — Cl -h  HOH. 

H H H 

That  the  ions  of  water  first  add  to  ammonia  is  rendered  improbable  from  the  fact 
that  NHi  itself  is  not  an  ion. 

When  water  acts  on  calcium  oxide  and  other  oxides  of  both  metals  and  nonmetals, 
it  is  difficult  to  conceive  of  the  mechanics  of  the  action  on  the  basis  of  ionization  since 
the  oxides  themselves  are  not  ions  and  water  is  ionized  to  the  extent  of  only  2 mg. 
of  hydrogen  to  a ton  of  water.  Furthermore,  kinetic  action  is  precluded  because 
water  does  not  decompose  below  1000°.  In  accordance  with  the  above  principles, 
however,  the  action  is  readily  explained  as  follows; 

/OH 

Ca=0=  =0— H — >-  Ca( 

I ^OH 

H 

Whereas  molecular  affinity  is  recognized  in  hydrated  salts  and  other  compounds, 
its  rational  apphcation  here  necessitates  an  assumption  of  the  tetravalency  of  oxygen. 
The  position  of  oxygen  in  the  periodic  system,  the  variability  of  valency  of  its  closest 
analogue,  sulphur,  and  the  necessary  postulate  of  a higher  valency  of  oxygen  to  ex- 
plain water  of  crystalUzation  and  the  addition  products  of  alcohols,  ethers,  etc., 
clearly  entitles  oxygen  to  an  occasional  higher  valency  than  two. 

2 This  Journal,  35,  24. 


Reactions  of  the  Arsines. 


95 


tion  of  the  nitrate  is  easily  deduced.  The  sulphate  gave,  as 
the  main  end  products,  cacodyl  sulphide  (and  cacodylic  acid), 

(CH,),As— H 

i\ 

therefore,  the  structure  ^ q ^SO.,  is  probable,  sul- 

1/ 

(CH3),As-H 

phur  being  hound  to  arsenic.  Analogously,  nitrogen  is  prob- 
ably hound  directly  to  arsenic,  as  is  shown  in  the  formula 
(CH,),As-H 

/\  . Under  the  influence  of  heat'  (internal  kinetic 

H— O NO2 

dissociation),  this  compound  could  split  off  nitrous  acid. 


(CH3)2As H 

I 

O 


(CH3)2As  4-  H 

I 

O , 


HO 


NNO 


H— O 


NO 


forming  dimethylhydroxylarsine,^  which  would  react  with 
more  nitric  acid,  as  follows: 


(CH3)3As— O— H 

II 

>0 

^O 


H— O— N 


(CH3)3As— OH 

/\ 

/ \ 

HO  Nf 


(CH3),As  = 0- — H ->  (RH,)3As  = 0 H 

/\/  ^ I ? 

H— O N = 0 H— O N = 0; 

and  thus  satisfactorily  explain  the  formation  of  cacodylic 
acid,  the  main  end  product. 

The  above  described  action  of  nitric  acid  illustrates  that 


1 It  must  be  remembered  that  dissociations  may  be  induced  not  only  by  heat, 
light,  and  other  forces,  but  also  by  various  reagents.  Since  the  latter  really  involve 
other  chemical  changes  the  term  dissociation  is  used  herein  to  indicate  decompositions 
induced  by  heat  only. 

^ This  compound  probably  has  no  separate  existence  since,  under  conditions 
favoring  its  formation,  its  anhydrous  form,  cacodylic  oxide,  R2ASOASR2,  is  always 
obtained  (Baeyer:  Ann.  Chem.  (Liebig),  107,  282).  However,  since  cacodylic  oxide 
is  proved  (This  Journal,  35,  9-14)  to  be  an  oxidation  product  of  dimethylarsine 
the  above  conclusions  are  justified. 


96 


Dehn, 


the  process  of  oxidation  is  conditioned,  not  by  the  mere  presence 
of  oxygen  but  by  a facility  of  coalescence  of  the  reagent  with  the 
substance]  in  other  words,  the  reducing  power  of  the  arsines 
and  their  derivatives  is  conditioned  by  a capacity  for  pre- 
liminary molecular  linking;  at  any  rate,  most  reduction  pro- 
cesses of  the  arsines  thus  far  studied^  have  yielded  initial  molec- 
ular aggregates,  or  have  given  evidence  of  their  formation. 

A striking  example  of  this  action  of  the  arsenic  atom  is 
observed  in  the  formation  of  arsonic  acids,  when  sodium 
arsenite  is  treated  with  alkyl  iodides.  The  reaction 

NagAsOg  -f  RI  RAsOgNa^  + Nal 

was  discovered  by  Meyer^  and  was  described  by  him  as  “an 
anomalous  reaction,”  because  by  “double  decomposition”  it 
was  expected  that  an  alkyloxy  compound  would  be  formed. 
However,  it  was  found  that  the  alkyl  group  combines  di- 
rectly with  the  arsenic.  This  is  easily  explained  on  the  basis- 
of  initial  molecular  attraction;  the  arsenite  and  the  halide 
uniting,  rearranging,  and  decomposing  as  follows: 

NaO.  /O— Na  „ 

NaO— As=  =1— R — > >As— I — >Asf  .. 

Nao/  NaO/  ■ NaO/  \r 

Thus  it  is  seen  that  instead  of  being  an  “anomalous  reaction’^ 
it  may  be  considered  a beautiful  example  of  the  normal  reaction. 

From  the  foregoing  it  is  concluded  that  many  reactions  of 
the  arsine  compounds  can  best  be  explained  by  making  the 
following  assumptions: 

1.  Unsaturated  valencies  (partial  or  latent  valencies)  in, 
both  substances; 

2.  Molecular  coalescence  of  the  two  substances; 

3.  A condition  of  instability  established  in  the  molar  ag- 
gregate, owing  to  this  distribution  of  the  total  valencies  of  the 
nuclear  elements,  and  thus  inducing  either 

4.  A tendency  toward  reversible  reaction  or 

5.  A tendency  toward  rearrangement;  and  finally, 

J See  page  97. 

2 Ber.  d.  chem.  Ges.,  16,  1441. 


Reactions  of  the  Arsines.  97 

6.  A dissociation  of  the  molar  aggregate  into  its  more 
stable  components. 

• EXPERIMENTAL. 

7.  Electrolytic  Reduction  of  Arsine  Derivatives. 

These  experiments  were  undertaken  for  the  purpose  of 
demonstrating  the  formation  of  intermediate  products  when 
alkyl  arsenic  derivatives  are  reduced  to  free  arsines.  It  was 
found  hitherto  that  the  final  reduction  product  of  both  cacodyl 
chloride^  and  cacodyP  is  dimethylarsine ; it  is  now  proposed 
to  show  that  cacodyl  is  an  intermediate  product  of  the  reduc- 
tion of  cacodyl  chloride,  and  that  the  successive  reactions  are 
as  follows : 

2(CH3)2AsC1  + 2H  = (CH3)2As— As(CH3)2  -f  2HCI, 

(CH3)2As— As(CH3)2  -f-  2H  = 2(CH3)2AsH. 

After  a number  of  unsuccessful  experiments  with  porous  cells 
used  to  keep  the  anode  and  cathode  solutions  separate,  a cell  was 
devised  which  was  found  most  convenient,  not  only  for  ob- 
serving the  progress  of  the  reductions  but  also  for  experiment- 
ing with  small  quantities  of  material.  The  apparatus  used 
is  shown  in  Fig.  III. 

The  other  details  are  as  follows:  (a)  platinum  cathode 
spiral,  (b)  porous  clay  partition,  (c)  a packed  asbestos  ring, 
(d)  platinum  anode  plate,  (e)  glass  support  for  the  anode  plate, 
(/)  exit  for  anode  gas  and  intake  for  anode  solution,  (g)  drain 
for  anode  solution,  (h)  exit  for  cathode  gas,  (i)  intake  for 
cathode  solution. 

Method  of  Using. — The  cathode  solution  first  used  was  pre- 
pared by  mixing  5 grams  of  cacodyl  chloride,  90  grams  of 
formic  acid,  and  8 grams  of  alcohol;  its  specific  gravity  was 
1.08.  An  anode  solution  of  the  same  specific  gravity  was 
prepared  from  sulphuric  acid.  After  sufficient  anode  solu- 
tion and  II  cc.  of  cathode  solution  were  run  into  the  reduc- 
tion cell  and  all  the  parts  of  the  apparatus  were  adjusted,  a 
current  of  5 to  6 volts  and  o . 5 to  o . 6 ampere  was  turned  on.  The 
cathode  solution  clouded  almost  immediately  and  after  500 

1 Ber.  d.  chem.  Ges.,  27,  1378. 

^ This  Journal,  36,  3. 


98 


Dehn. 


cc.  of  electrolytic  hydrogen  had  been  evolved  in  the  voltameter, 
a heavy  oil  was  found  to  have  separated  in  the  cell  and  a 
spontaneously  inflammable  gas  began  to  be  evolved  with  the 
cathode  hydrogen — this  gas  increased  in  concentration  during 
the  remainder  of  the  reduction.  The  oil,  insoluble  in  formic 
acid,  was  identified  as  cacodyl;  the  gas  was  found  to  be  di- 
methylarsine ; hence  the  above  equations  are  established. 


A.  A Hofmann  U-tube  placed  in  series  with  the  cell  and  used  as  a hydrogen  volta- 
meter. 

B.  The  reduction  cell,  made  of  glass. 

C.  Apparatus  used  to  measure  the  gas  evolved  at  the  cathode  and  subsequently 

to  deliver  into  Hempel  burettes  (at  point  fe). 

The  following  experiment  was  undertaken  for  the  purpose 
of  determining  the  relative  rates  of  reduction  of  cacodyl  chlor- 
ide to  cacodyl,  and  of  the  latter  to  dimethylarsine : 

The  cathode  solution  was  prepared  by  dissolving  9 . i grams 
of  cacodyl  chloride  in  a mixture  of  90  cc.  of  alcohol  and  25  cc. 
of  hydrochloric  acid  (sp.  gr.  1.2);  one  fifth  of  this  solution 
and  a current  of  5 to  6 volts  and  1.05  to  1.20  amperes  were 
used  for  the  reduction.  When  exactly  50  cc.  of  hydrogen  had 


Reactions  of  the  Arsines. 


99 


been  evolved  in  the  voltameter  (II.) , the  current  was  turned 
off  and  the  volume  of  mixed  gases  (III.)  evolved  from  the 
cathode  solution  was  measured  in  the  apparatus  C;  the  gas 
was  next  drawn  over  into  a Hempel  burette  containing  silver 
nitrate  solution  and,  after  shaking,  the  volume  of  the  residual 
gas  (unfixed  hydrogen)  was  measured  (V.)  The  loss  in  vol- 
ume at  this  point  represented  an  equivalent  volume  of  di- 
me thylarsine  gas  and  one  half  of  this  volume  was  equivalent 
to  the  volume  of  hydrogen  fixed  by  dime  thylarsine.  Fifty 
cc.  of  hydrogen,  minus  the  volume  of  unfixed  residual  hydro- 
gen and  the  hydrogen  fixed  by  dimethylarsine,  represented  the 
volume  of  hydrogen  fixed  by  cacodyl,  according  to  the  equation 


2(CH3)2AsC1  + H2  = [(CH3)2As]2  -h  2HCI. 
Reduction  of  Cacodyl  Chloride. 


I. 

II. 

III. 

IV. 

50  cc.  minus 

V. 

Residual 

VI. 

Di- 

VII. 

Hydrogen 

VIII. 

Hydrogen 

No*  of  ex- 

Total hy- 

Burette 

burette 

gas 

methyl- 

fixed  by 

fixed  by 

periment. 

drogen. 

gas. 

gas. 

(AgNOs). 

arsine. 

(CH3)2AsH. 

cacodyl. 

I 

50 

2.5 

47.5 

2.5 

0.0 

0.0 

47.5 

2 

100 

5.1 

44-9 

50 

0.  I 

0.0 

450 

3 

150 

7-9 

42.1 

7-9 

0.0 

0.0 

42.1 

4 

200 

II. 9 

38.1 

II. 8 

0.  I 

0. 1 

38.1 

5 

250 

15.9 

34-1 

15-7 

0.2 

0. 1 

34-2 

6 

300 

20.4 

29.6 

19.7 

0.7 

0-3 

30.0 

7 

350 

25.0 

25.0 

24.2 

0.8 

0.4 

25-4 

8 

400 

304 

19.6 

293 

I . I 

0.6 

20. 1 

9 

450 

36.3 

137 

34-3 

2.0 

1 .0 

14-7 

10 

500 

413 

8.7 

38.9 

2.4 

I .2 

9 9 

II 

550 

44-5 

5-5 

40.5 

4.0 

2.0 

7-5 

12 

600 

45-3 

4.7 

39-6 

5.7 

2.9 

7-5 

13 

650 

47-5 

2.5 

40.4 

7.1 

3-6 

6.0 

14 

700 

48.6 

1.4 

41.2 

7-4 

3-7 

51 

15 

750 

50.1 

— 0. 1 

40.9 

9.2 

4.6 

4-5 

16 

800 

50.8 

—0.8 

40.7 

10. 1 

51 

4.2 

17 

850 

52.2 

— 2 . 2 

41.9 

10.3 

5-2 

2.9 

18 

900 

52.2 

— 2 . 2 

42 . 2 

10. 0 

50 

2.8 

19 

950 

52.4 

—2.4 

42 . 2 

10 . 2 

51 

2.7 

20 

1000 

52.2 

— 2 . 2 

42.1 

10. 1 

50 

2.9 

22 

1 100 

52.0 

— 2 .0 

42.8 

9.2 

4.6 

2 . 6 

24 

1200 

51.0 

— 1 .0 

43-9 

7.1 

3-5 

2 . 6 

26 

1300 

50.9 

—0.9 

45-1 

5.8 

2.8 

2 . 1 

28 

1400 

510 

— 1 .0 

45-9 

51 

2 . 6 

1-5 

30 

1500 

515 

—1-5 

47.0 

3-5 

1-7 

13 

32 

1600 

50.7 

— 0.7 

48 . 2 

2-5 

1 . 2 

0.6 

34 

1700 

50.1 

— 0. 1 

49.0 

I . I 

0.6 

0.4 

lOO 


Dehn. 


It  may  be  observed  in  the  table:  that  the  volume  of  gases 
evolved  from  the  cathode  solution,  at  first,  is  much  less  than 
the  volume  of  the  voltameter  hydrogen  collected  during  the 
same  interval  of  reduction;  then,  at  about  the  middle  of  the 
series  of  reductions,  it  becomes  equal  to  the  voltameter  hy- 
drogen ; during  most  of  the  remainder  of  the  reductions,  the 
cathode  gas  volume  is  greater  than  the  voltameter  hydrogen; 
but  finally,  it  becomes  just  equal  to  it.  When  cacodyl  alone 
is  formed,  the  residual  hydrogen  must  be  less  than  the  volt- 
ameter hydrogen,  owing  to  the  fixing  of  hydrogen  (the  product 
being  hydrochloric  acid),  as  shown  in  the  above  equation. 
When  dimethylarsine  alone  is  formed  by  the  reaction, 

(CH3)3As-As(CH3)3  + H3  = 2(CH3)3AsH, 

the  total  volume  of  gas  evolved  must  be  greater  than  the  volt- 
ameter hydrogen — two  volumes  of  arsine  resulting  from  one 
volume  of  hydrogen.  Therefore,  when  both  cacodyl  and  di- 
methylarsine are  being  formed,  the  burette  gas  represents 
the  algebraic  sum  of  these  two  reductions;  and,  depending 
upon  the  proportion  of  the  two  products,  may  be  less  or  greater 
than  the  voltameter  hydrogen.  With  the  cubic  centimeters 
of  “fixed”  hydrogen  as  ordinates  and  the  quantity  of  elec- 
tricity, measured  in  50  cc.  of  hydrogen,  as  abscissas,  (i) 
the  composite  curve  of  reduction,  (2)  the  dimethylarsine 
curve,  and  (3)  the  cacodyl  curve  may  be  plotted,  as  shown 
in  Fig.  IV. 

It  will  be  seen  that  when  the  composite  curve  of  reduction 
crosses  the  base  line,  the  quantity  of  arsine  is  just  twice  that 
of  the  cacodyl. 

As  plotted,  the  area  included  within  the  cacodyl  and  di- 
methylarsine curves  represents  the  total  quantity  of  hydrogen 
fixed",  the  area  included  between  the  base  line  and  a parallel 
line  at  50  cc.  represents  the  total  electrolytic  hydrogen. 

From  a consideration  of  the  above  experiments  it  may  be 
anticipated  that  when  cacodyl  itself  is  reduced,  the  composite 
curve  of  reduction  becomes  coincident  with  the  dimethylarsine 
curve.  This  is  confirmed  by  the  following  experiment.  A cathode 
solution  was  prepared  by  dissolving  5 cc.  of  crude  cacodyl 


Reactions  of  the  Arsines. 


lOI 


in  a mixture  of  50  cc.  of  alcohol  and  25  cc.  of  hydrochloric 
acid  (sp.  gr.  1.20).  With  a current  of  5 to  6 volts  and  i.o 
to  o . 6 ampere,  20  cc.  of  this  solution  were  reduced  in  the  man- 
ner described  above. 


Reduction  of  Cacodyl. 


I. 

II. 

III. 

IV. 

50  cc.  minus 

V. 

Residual 

VI. 

Number  of 

Total 

Burette 

burette 

gas 

Dimethyl- 

experiment. 

hydrogen. 

gas. 

gas. 

(AgNOs). 

arsine. 

I 

50 

36.0 

14.0 

36.0 

0.0 

2 

100 

37-4 

12.6 

37-3 

0.  I 

3 

150 

38.9 

II  . I 

38.5 

0.4 

4 

200 

40.3 

9-7 

39-6 

0.7 

5 

250 

41 . 8 

8.2  . 

41. 1 

0.7 

6 

300 

43-6 

6.4 

42 . 6 

I .0 

7 

350 

46.2 

3.8 

44.8 

1.4 

8 

400 

47.6 

2.4 

45-7 

1-9 

9 

450 

49  I 

0.9 

46.6 

2.5 

10 

500 

50.4 

— 0.4 

47.0 

3-4 

II 

550 

52.0 

2 .0 

48 .0 

4.0 

12 

600 

52.8 

—2.8 

49  0 

3-8 

13 

650 

540 

—4.0 

49.0 

50 

14 

700 

550 

—5.0 

49.8 

5-2 

15 

750 

55-6 

—5.6 

50.1 

5-5 

102 


Dehn. 


Reduction  of  Cacodyl — {Continued), 


Number  of 
experiment. 

16 

17 

18 
20 
22 
24 

26 

28 

30 


II. 

Total 

hydrogen. 

800 
850 
900 
1000 
1 100 
1200 
1300 
1400 
1500 


III. 

Burette 

gas. 

55-9 

55.8 

55-7 
55  I 
53-9 

52.8 

51.8 

50.8 
50.2 


IV. 


V. 


50  cc.  minus  Residual 


burette 

gas. 

—5-9 

—5.8 

—5-7 

—51 

—3-9 
— 2 . 8 
—1.8 
—0.8 
+0.2 


gas 

(AgNOs). 


50 

50 

50 

50 

49 

49 

49 

49 

50 


VI. 

Dimethyl- 

arsine. 

5-6 
5-5 
5-4 
4.6 
4.0 
30 
2 .0 
0.9 
o.  I 


That  the  burette  readings  were  not  immediately  greater 
than  the  voltameter  readings  or,  in  other  words,  that  the  com- 
posite curve  of  reduction  was  not  more  nearly  coincident 
with  the  dimethylarsine  curve,  is  explained  by  the  facts  (i) 
that  it  is  almost  impossible  to  prepare  and  to  handle  pure 
cacodyl  without  its  becoming  oxidized,  (2)  crude  cacodyl 
contains  large  quantities  of  cacodylic  oxide,  and  (3)  dimethyl- 
arsine is  somewhat  soluble  in  the  above  mentioned  cathode 


Reactions  of  the  Arsines. 


103 


solution.  However,  the  curves  show  sufficiently  well  that 
cacodyl  is  electrolytically  reduced  to  dimethylarsine. 

In  view  of  the  above  experiments  and  since  dimethylarsine 
is  easily  prepared  from  cacodylic  acid  by  reduction  with  zinc 
and  hydrochloric  acid,  it  might  be  supposed  that  the  elec- 
tric current  would  induce  the  same  reaction: 

(CH3)2AsOOH  + 4H  = (CH3)2AsH  + 2H2O. 

However,  experiments  showed  that  no  arsine  was  evolved; 
an  explanation  of  this  is  seen  in  the  following  equations: 

(CH3)2As02H  = (CH3)2As03  + H, 

2(CH3)2As02  + H2O  = 2(CH3)2As02H  -f  O. 

11.  Primary  Arsines. 

With  Elrick  Williams. 

Studies  with  Gaseous  Primary  Meihylarsine. 

The  sodium  salt  of  methylarsonic  acid^  was  reduced  by  zinc 
and  hydrochloric  acid-  and  the  mixture  of  hydrogen  and  gas- 
eous methylarsine  was  passed  into  a large  bottle  filled  with  water 
and  so  arranged  that  the  gaseous  mixture  could  both  be  pre- 
served free  from  oxidation  and  also  so  that  portions  of  it, 
as  desired,  could  be  drawn  off  into  Hempel  burettes.  Usually 
the  gaseous  mixture  was  drawn  out  by  depressing  the  com- 
panion tube  of  the  Hempel  burette;  then  boiled  water  was 
permitted  to  run  into  the  gas  reservoir,  so  as  to  equalize  the 
interior  and  exterior  pressures.  Samples  of  the  gas  in  the 
Hempel  tube  were  treated  with  solutions  as  indicated  in  the 
following  table  of  preliminary  experiments;  from  time  to  time 
the  concentration  of  the  arsine  in  the  reservoir  was  determined 
by  treatment  with  silver  nitrate  solution.^ 

1 Ann.  Chem.  (Liebig),  249,  147. 

2 This  Journal,  33,  120. 

» Ibid.,  33,  125. 


104 


Dehn, 


o 


•ti  o 


a> 

4-> 

d 
+-> 

*o  . 

a.2 

-M 

^ d 

0 <u 

2 ’d 

1 05 

2 

w 


. 5=! 

bjo  oJ 

•So 

t/i 

S o 

o ^ 

^ O 

S 0) 

Vi 

2g 

• dt 

Tt- 


X U3 

O (1> 

W) 

o 

P<’T3 

o 

u 

o 


^ t/i 

■i->  <v 


d 


‘^.2^0 
o ^ 
„ ^ o 

2^0.4^ 
CJ  o 
G 

^ ^ ’d 
Q.d  o 

a 


d 

;-i 

. OJ 

T3 

2 

G ^ 
S G 

1 

. a 

G 

G ^ 
^ O 

3 

ffi 

d, 

•-..d  g^:: 
^-g  do 


t s. 

JS*  t/i 

^ S.’S 
<5  ^"S 

X°  8 

S4i  §■• 

o 

d G 
5 2 


O (D 


<U  > . 

d 

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& >■  W 

*o  .' 

<U  r-i 

u O 

Pnxn 


><  § 


to  53 
K p^ 

2 d 

^ 2 o 

S -*->  CO 

$ w ^ 

^ G rr<^  G 

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g-^ 


oi  >• 

„ c^  d 
a>  > 
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6 

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So-'^ 

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CJ  . 

K-.  O 


a 

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2 

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G •“ 
bJOTJ 


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^ CO  CO  G 

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CO  bJD  bO'+H 

G^^  O 
2 G G - 
rG  2 G d 


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Time 
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Si  ^ go” 

t3ffi  8 85 


ro  lO 


Sn  ^ 'G 

a 

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pq. 

Ph  c/5 

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20 

21 

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to 


23  PbO; 


Reactions  oj  the  Arsines.  - 105 

Interpretations  of  the  above  data  render  probable  the  fol- 
lowing equations: 

1.  6KMn04  + 5RASH2  = 

6MnO  + 3RASO3K2  + 2RASO3H2  + 3H2O. 

2.  6KMn04  + 5RASH2  = 

qMnO  + 3RASO3K2  + 2RAs03Mn  H-  5H2O. 

3.  4K3Fe(CN)«  + RASH2  + H2O  = 

3K4Fe(CN)6  + H4Fe(CN)e  + RAsO.^ 

4.  4FeCl3  + RASH2  + H2O  = 4FeCl2  + 4HCI  RAsO.^ 

5.  4Pb(AC)2  RASH2  + 3H2O  = 

3Pb  + 8HC2H3O2  + RAsOgPb.^ 

6.  K2Cr207  + RASH2  = (See  This  Journal,  35,  28). 

7.  6H2Cr04  + 2RASH2  = 

3(2Cr02.H20)  + 2RASO3H2  + 3H20.^ 

8.  2H2O2  + RASH2  = RAsO  + 3H2O. 

9.  3Br2  + RASH2  + 3H2O  = RASO3H2  + 6HBr.'‘ 

10.  HgCl2  + RASH2  = RAsHHgCl.HCl  (etc.).' 

11.  CUSO4  + RASH2  = RAsH2.CuS04(?), 

12.  6HNO2  + RASH2  = RASO3H2  4-  6NO  + 3H20.« 

13.  H2SO4  + RASH2  = RASH2.H2SO4.’ 

14.  HNO3  + RASH2  = (See  This  Journal,  33,  125;  35,  27). 

15.  SbCl3  + RASH2  = (Seepage  112). 

16.  ASCI3  + RASH2  = Seepage  iii). 

17.  (CH3)2AsC1  + RASH2  = (See  page  122). 

18.  (CH3)2AsiVs (0113)2  + RASH2  = No  reaction. 

19.  SnCl4  + RASH2  = (Seepage  no). 

20.  PCI3  -f  RASH2  =*=  (Seepage  in). 

21.  S2CI2  + RASH2  = RASCI2  + S + H2vS.« 

22.  SO2  + RASH2  = (See  This  Journal,  35,  38). 

23.  Pb02  + RASH2  = (See  This  Journal,  35,  30). 

1 Cf.  This  Journal  35,  35. 

2 Ibid.,  35,  30. 

3 Ibid.,  35,  28. 

“ 33,  126;  35,  14. 

^Ibid.,  33,  127;  35,  35. 

Ibid.,  35,  26. 

7 Ibid.,  35,  24. 

^ Ibid.,  35,  39. 


io6 


Dehn. 


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2 36,  2.5. 

3 Jbtd.,  35,  26. 


Reactions  of  the  Arsines. 


107 


Hydriodic  Acid  and  Methylarsine. — A mixture  of  50.4  cc. 
of  gaseous  methylarsine  (8.1  cc.)  and  hydrogen  (42.3  cc.), 
treated  over  mercury  with  i cc.  of  concentrated  aqueous  hy- 
driodic acid,  increased  2 cc.  in  volume  in  20  minutes;  after 
heating  for  20  minutes  more  at  100°,  an  increase  of  10.9  cc. 
in  volume  resulted.  The  gaseous  mixture,  after  cooling  to 
the  original  temperature,  was  treated  with  a solution  of  silver 
nitrate — a decrease  in  volume  of  6.7  cc.  resulted.  From  these 
experiments  it  is  concluded  that  the  following  reactions  are 
slow^  or  are  easily  reversible: 

CH3ASH2  + HI  CH3ASH3I  — ^ CH3ASHI  + H2, 

CH3ASHI  + HI  CH3ASH2I2  CH3ASI2  + H2. 

Propyl  Iodide  and  Methylarsine. — When  a gaseous  mixture  of 
75.5  cc.  of  methylarsine  (lo.i  cc.)  and  hydrogen  (63.4  cc.),  with 
I cc.  of  liquid  n-propyl  iodide,  was  heated  for  one  hour  at  ioo° 
in  a mercury  eudiometer,  a decrease  in  volume  of  4 cc.  was  ob- 
served on  cooling  to  the  original  temperature.  When  treated 
with  silver  nitrate  solution,  the  residual  gas  suffered  a loss  of 
5.8  cc.  (unchanged  methylarsine).  During  the  experiment, 
light  yellow  crystals  (melting  below  100°)  were  observed  on  the 
walls  of  the  eudiometer;  therefore  the  following  equation  is 
justified 

CH3ASH2  + C3H7I  (CH3)(C3H7)AsH2l. 

Silver  Nitrate  and  Methylarsine.^ — The  black  precipitate  in  a 
gas  burette,  after  treatment  of  a silver  nitrate  solution  with 
quantities  of  methylarsine,  was  washed  with  water  and  dried  at 
100°. 

0.5439  gram  of  substance  gave  0.4430  gram  of  AgCl. 

, Calculated  for 

CH8As03Ag2.  Found. 

Ag  60 .69  79 . 90 

Since  methylarsonic  acid  was  found  in  the  precipitate,  the 
latter  is  evidently  a mixture  of  metallic  silver  and  silver  methyl- 
arsonate. 

1 Cf.  This  Journal,  36,  27. 

2 Addition  products  are  almost  invariably  observed  when  primary,  secondary, 
and  tertiary  arsines  are  treated  with  alkyl  iodides.  Cf.  This  Joxjrnal,  33,  128,  and 
see  pages  121,  122,  and  123. 

3 Cf.  This  Journal,  33,  126;  36,  35. 


io8 


Dehn. 


Methylarsine  Oxide  and  Methylarsine. — When  the  white 
methylarsine  oxide,  formed  on  the  walls  of  a Hempel  burette 
by  the  reaction  of  atmospheric  oxygen  with  methylarsine,  was 
treated  with  gaseous  methylarsine,  all  of  the  methylarsine  was 
fixed  and  a brick  red  solid  replaced  the  white  oxide.  Evi- 
dently the  following  reaction : 

2CH3ASO  -f  2CH3ASH2  ->  (CH3As)4  -1-  2H2O; 

explains  the  formation  of  the  red  polymers  always  formed 
by  the  spontaneous  oxidation  of  the  arsines.  The  details  of  the 
reaction  are  shown  as  follows : 

CH,— As=0  CH3— As— OH  CH,— As 

!!  ->  I -^1  +H,0; 

CH3— As^H^  CH,— As— H CH3— As 

two  groups,  CH3 — As — As — CH3,  condensing  and  evidently 
forming  CH3 — As — ^As — CH3 

CH,— As— As— CH3’ 

The  following  substances  failed  to  react  with  gaseous  methyl- 
arsine: hydrogen  sulphide,  yellow  ammonium  sulphide,  potas- 
sium nitrite,  potassium  hydroxide,  nickelous  chloride,  formal- 
dehyde, acetic  acid,  aniline,  nitrobenzene,  and  benzotrichloride. 

Reactions  of  Ethylarsine. 

Iodine, — When  equimolecular  quantities  of  the  two  substances 
were  brought  together  in  a sealed  tube  containing  ether,  the 
color  of  the  iodine  was  quickly  discharged  and  a golden  yellow 
solution  resulted.  Hydrogen  and  an  oil  boiling  at  205®  to  210® 
and  containing  63.8  per  cent  of  iodine  (calculated  for  CjHjAsI,' 
is  70.9  per  cent)  were  obtained.  The  following  equation  is 
justified : 

C3H3ASH3  + I3  =-  C3H3ASI3  + H^. 

Bromine. — When  equimolecular  quantities  of  ethylarsine 
and  bromine  were  brought  together  in  ether,  a red  brown,  amor- 
phous solid  was  formed  immediately  and  remained  permanently 
(one  year)  undissolved.  Considerable  pressure  (hydrogen) 


Ann.  Chem.  (Liebig),  Hi,  367. 


Reactions  of  the  Arsines. 


109 


was  observed  on  opening  the  tube;  the  ether  solution  yielded,  by 
distillation,  an  oil,  ethylarsine  dibromide,  boiling  at  192°. 

0.4120  gram  substance  gave  0.5812  gram  AgBr. 

Calculated  for 

C2H5AsBr2.  Found. 

Br  60.60  60.03 

When  treated  with  platinic  chloride  the  dibromide  liberated 
heat  and  slowly  formed  yellow  white  crystals,  which  were  dried 
on  the  water  bath  and  ignited. 

0.8622  gram  substance  gave  0.2700  gram  Pt. 

Calculated  for 

C2HBAsBr2.PtCl4.i  Found. 

Pt  32.68  31.31 

The  brown  residue  from  the  sealed  tube  experiment  was 
analyzed : 

o.  1865  gram  substance  gave  0.0260  gram  AgBr. 


0.2106 

i < < 

“ 0 . 2247  gram  Mg2As207. 

Calculated  for 

(C2H5As)4. 

C2H5AsHBr. 

Found. 

Br 

0.00 

> 43-24 

10.25 

As 

72.11 

40.54 

51.62 

Evidently  this  shbstance  is  a mixture.  The  end  reaction  of  the 
arsine  with  bromine  is  as  follows : 

C2H5ASH2  + Br2  = C2H5AsBr2  + H2; 
while  positive  evidence  of  intermediate  products  is  deduced. 

Sulphur. — When  2 grams  of  ethylarsine  (i  mol.)  and  1.2 
grams  of  sulphur  (2  atoms)  were  brought  together  in  a sealed 
tube  filled  with  carbon  dioxide,  the  sulphur  was  seen  to  dissolve 
rapidly,  and  to  yield  a viscid,  colorless  liquid.  On  opening  the 
tube,  great  pressure  (hydrogen  sulphide,  but  no  hydrogen)  was 
observed.  The  percentage  of  sulphur  in  the  gluelike  mass  was 
determined : 

0.1962  gram  substance  gave  0.3475  gram  BaS04. 

Calculated  for 

CJH5ASS2.  C2H6ASS.  Found. 

s 38.09  23.52  24.28 

1 Cf.  This  Journal,  36,  32. 


no 


Dehn. 


Evidently  the  substance  is  ethylarsine  sulphide  with  an  admix- 
ture of  free  sulphur  or  the  disulphide,  and  the  original  reaction 
is  as  follows: 

C2H5ASH2  + 82  = C2H5ASS  + HgS. 

Mercuric  Chloride. — When  equimolecular  quantities  of  the 
two  substances  were  brought  together  in  a sealed  tube  filled 
with  carbon  dioxide,  a dark  yellow  black  precipitate  formed  im- 
mediately. and  changed  after  a time  to  a compact,  finely  divided, 
black  precipitate.  On  opening  the  tube  no  hydrogen  or  mer- 
curous chloride,  but  gaseous  hydrochloric  acid  and  metallic 
mercury  were  found.  An  ether  solution  of  the  oil  became 
yellow  red  in  the  air  and  ethylarsine  dichloride  was  detected  in 
the  ether  solution,  therefore  the  final  reaction  is  expressed  by 
the  following  equation 

C2H5ASH2  + 2HgCl2  = C2H5ASCI2  + 2Hg  + 2HCI. 

Mercuric  Iodide. — When  2.5  grams  of  ethylarsine  (i  mol.) 
and  10.7  grams  of  mercuric  iodide  (i  mol.)  were  brought  to- 
gether in  ether  contained  in  a sealed  tube,  a bright  yellow  product 
was  formed  immediately.  On  opening  the  tube  hydrogen,  mer- 
curous iodide  (4  grams — calculated,  7.7  grams),  and  an  oil  (5.7 
grams)  were  obtained ; the  oil  showed  the  presence  of  ethylarsine 
diiodide,  therefore  the  reaction  here  is  as  follows : 

C2H,AsH2  + 2Hgl2  = C2H5ASI2  + 2HgI  + H3. 

Stannic  Chloride. — When  2.14  grams  of  ethylarsine  (i  mol.) 
and  5.9  grams  of  stannic  chloride  (i  mol.)  were  sealed  with 
ether  in  a tube,  no  solid  formed  even  after  standing  for  14 
months.  No  pressure  was  observed  on  opening  the  tube;  the 
greenish  yellow  solution  was  concentrated  and  then  treated 
with  water;  the  aqueous  solution  contained  the  Sn"  ion  and 
the  oil  separating  was  found  to  distil  at  156°  (ethylarsine  di- 
chloride boils  at  156°).^  The  formation  of  the  end  products  is 
explained  by  the  equation 

C2H5ASH2  + 2SnCl4  = C2H5ASCI2  + 2SnCl2  + 2HCI, 

1 See  page  104,  and  cf.  This  Journal,  33,  127;  35,  35. 

2 La  Coste:  Ann.  Chem.  (Liebig),  208,  33. 


Reactions  of  the  Arsines,  iii 

though  evidence  of  intermediate  products*  was  manifest  in 
the  oil  separated. 

Phosphorus  Trichloride. — When  equimolecular  quantities  of 
the  two  substances  were  brought  together  in  an  ether  solution 
contained  in  a sealed  tube,  a fine  yellow  powder  separated  slowly. 
After  14  months  the  tube  was  opened;  gaseous  hydrochloric 
acid,  ethylarsine  dichloride,  and  a yellow  orange  solid  were  ob- 
tained. The  residue  persisted  in  giving  off  the  odor  of  ethyl- 
arsine dichloride  even  though  washed  repeatedly  with  ether; 
the  main  ether  solution,  on  being  shaken  with  solid  calcium 
chloride,  gave  a voluminous  precipitate  of  a red  brown  sub- 
stance. Evidently  there  was  in  solution  some  substance  other 
than  the  free  original  compounds  or  the  end  product,  ethyl- 
arsine dichloride. 

Arsenic  Trichloride. — When  equimolecular  quantities  of  the 
two  substances  were  brought  together  in  a sealed  tube  contain- 
ing ether,  a yellow  solid  appeared  and  changed  rapidly  to  a 
curdy,  brick  red  solid.  Ethylarsine  dichloride  was  found  in  the 
ether  solution ; the  residue  was  analyzed  for  arsenic : 

0.1387  gram  substance  gave  0.2214  gram  Mg2As207. 

Calculated  for 

(C2H5As)a:.  Found. 

As  72.11  77-24 

Evidently  this  residue  is  a mixture  of  the  polymer  (C2H5As)^ 
with  metallic  arsenic  and  the  equation  representing  the  reaction 
is 

8C2H5ASH2  + 8ASCI3  = 4C2H5ASCI2  + 16HCI+  8AS.2 

Antimony  Trichloride. — When  equimolecular  quantities  of 
the  two  substances  were  brought  together  in  a sealed  tube  con- 
taining ether,  a red  brown,  amorphous  solid  was  formed  imme- 
diately, but  in  the  course  of  14  months  it  changed  to  a jet 
black  solid.  Considerable  pressure  of  gaseous  hydrochloric  acid 
was  observed  on  opening  the  tube.  The  ether  solution  yielded 
ethylarsine  dichloride  and  a little  unchanged  antimony  tri- 
chloride ; the  black  residue  was  washed  repeatedly  with  ether  but, 

1 Cf.  This  Journal,  35,  39. 

2 Cf  page  126. 


II2 


Dehn, 


on  drying,  inflamed  spontaneously.  Unquestionably  interme- 
diate products  were  formed  in  this  experiment. 

Water. — When  2 grams  of  ethylarsine  and  5 grams  of  water 
were  heated  in  a sealed  tube  for  six  hours  at  180°,  no  evidence 
of  a reaction  could  be  observed. 

Hydrochloric  Acid  Solution. — When  ethylarsine  was  treated 
with  an  excess  of  one  molecule  of  hydrochloric  acid  (sp.  gr.  1.20) 
and  the  mixture  was  heated  for  two  hours  at  70°,  no  evidence 
of  a reaction  could  be  observed. 

Isopropyl  Iodide  and  Ethylarsine. — When  3.7  grams  of  ethyl- 
arsine and  18  grams  of  isopropyl  iodide  were  heated  to  70°  for 
one  hour  in  a sealed  tube  filled  with  carbon  dioxide,  no  conden- 
sation was  observed;  after  heating  for  three  hours  at  110°,  a 
dark,  red  brown  oil  was  obtained.  The  arsonium  iodide  (90 
per  cent)  was  separated  in  the  usual  manner;  0.2450  gram  re- 
quired 0.1155  gram  of  AgNOg  = 35.22  per  cent  iodine;  calcu- 
lated, 35.18  per  cent. 

When  a sample  of  0.0546  gram  of  the  triisopropylethylar- 
sonium  iodide  was  heated  in  the  tensimeter  molecular  weight 


apparatus^ 

the  following  data  were 

obtained : 

Vapor 

Vapor 

Apparent 

Theoretical 

t. 

pressure. 

volume. 

mol.  wt. 

mol.  wt. 

130 

0.0 

0.0 

360 

179 

I . 2 

0.007 

198 

8.3 

0.044 

234 

388.3 

2.066 

411.6 

240 

1092.0 

2.578 

279.0 

262 

2138.0 

3.428 

14^'  5 

The  volume  of  nonreversible  vapor  at  28°  was  2.7  cc. ; it  burned 
with  a luminous  flame,  was  free  from  arsenic  and  iodine,  and 
was  not  affected  by  bromine  water.  On  cooling,  the  residue,, 
possessing  an  odor  of  tertiary  arsine,  consisted  of  a red  yellow 
oil  and  light  yellow  crystals;  the  product  reacted  strongly  with 
bromine  water.  Evidently  triisopropylethylarsonium  iodide 
decomposes  at  its  melting  point,  according  to  the  following  re- 
actions : 

(03117)3(02155)  Asl  = (03117)3 As  -f  02HgI, 

2(03H7)302H5AsI  = (03H7)3ASI2  + O^H^o  + (03H7)3As. 

1 J.  Am.  Chem.  Soc.,  29,  1052. 


Reactions  of  the  Arsines, 


113 

n-Propyl  Iodide  and  Ethylarsine. — When  2 grams  of  ethyl- 
arsine  and  10  grams  of  rt-propyl  iodide  were  sealed  in  tubes 
filled  with  carbon  dioxide  and  heated  for  one  hour  at  70°,  no 
effect  was  observed;  heated  for  three  hours  at  110°,  much  pres- 
sure (hydrogen)  and  a red  oil  were  observed.  Tri-n-propyl- 
ethylarsonmm  iodide  was  separated  and  found  to  soften  at  230° 
and  melt  at  237°,  with  decomposition.  An  alcoholic  solu- 
tion of  the  iodide  treated  with  an  alcoholic  solution  of  mercuric 
iodide  gave  a light,  yellow  white  precipitate,  which,  after  re- 
crystallizing from  alcohol,  gave,  on  analysis,  22.09  cent  of 
iodine;  calculated  for  (C2H5)(C3H7)3AsHgI  = 22.64  pcr  cent.^ 

Propylarsine. 

M-Propylarsonic  acid^  (95  grams)  and  amalgamated  zinc  dust 
(500  grams)  were  placed  in  a flask  and  treated  with  concen- 
trated hydrochloric  acid,  in  the  usual  manner;®  the  propyl- 
arsine was  condensed  in  a sulphur  dioxide  condenser  surrounded 
by  a freezing  mixture.  After  transferring  to  bulbs  of  the  proper 
size,  it  was  analyzed: 

0.1603  gram  substance  gave  0.1724  gram  CO2  and  0.1088 


gram  HjO. 

Calculated  for 

CsHtAsH,. 

Found. 

C 

7-50 

7.54 

H 

30.00 

Monobenzylarsine. 

29*33 

A 2 -liter,  hard  glass,  round  bottom  flask,  containing  52 
grams  of  benzylarsonic  acid,^  200  cc.  of  ether,  and  500  grams  of 
amalgamated  zinc  dust®  was  connected  with  a reflux  condenser, 
a dropping  funnel,  and  a mercury  valve;  concentrated  hydro- 
chloric acid  was  dropped  in  until  the  reduction  was  complete : 

C^HjCHjAsOsH^  H-  6H  - -h  3H2O. 

As  the  reduction  proceeded,  some  red  oxidation  product  was 
deposited  upon  the  inner  walls  of  the  flask  and  a distinct  odor 

1 Cf.  Ann.  Chem.  (LiebigX  S41,  182. 

* J.  Am.  Chem.  Soc.,  28,  352. 

3 This  Journal,  SS,  120;  95,  3. 

* J.  Am.  Chem.  Soc.,  38,  354. 

^ This  Journal,  99,  118. 


Dehn. 


114 

of  arsine  was  observed.  After  2 to  3 days,  more  ether  was 
added  and  the  flask  was  shaken,  then  water  was  admitted 
through  the  dropping  funnel  until  all  of  the  ether  solution 
(somewhat  green  in  color)  was  forced  up  into  a separatory 
funnel  containing  sticks  of  calcium  chloride  and  filled  with 
carbon  dioxide.  The  separatory  funnel  was  closed  and  shaken 
until  the  ether  solution  was  dried.  A Briihl  distilling  apparatus, 
properly  connected  with  a condenser,  a flask,  and  an  inverted 
TJ-shaped  delivery  tube,  was  partially  exhausted  by  means  of 
the  water  pump ; the  delivery  tube  with  proper  connections  was 
dipped  to  the  bottom  of  the  ether  solution  contained  in  the 
separatory  funnel  and  the  distilling  flask  was  about  half  filled 
with  the  ether  solution.  By  means  of  the  pump,  the  ether  solu- 
tion was  soon  concentrated,  then  more  of  it  was  drawn  in;  this 
process  was  repeated  until  all  of  the  ether  solution  had  been 
evaporated  at  room  temperature.  The  residual  liquid,  light 
yellow  in  color,  was  distilled,  and  the  following  fractions  were 
obtained : 


I. 

140° 

262  mm. 

8.5  grams 

2. 

140° 

260  “ 

4.1  “ 

3- 

141° 

260  “ 

3-2  “ 

The  residue  in  the  distilling  flask  changed  finally  and  rather 
abruptly  to  a dark  red  solid.  The  apparatus  was . then  filled 
with  carbon  dioxide  and  small  bulbs,  containing  carbon  dioxide, 
were  filled  with  the  different  fractions : 

0.1236  gram  of  fraction  (i)  gave  0.2260  gram  CO2  and  0.0602 
gram  H2O. 

Calculated  for 

C7H9ASH2.  Found. 

C 50.00  49-87 

H 5-35  5-41 

Benzylarsine  is  a faintly  yellow  liquid  boiling  at  140°  under 
262  mm.  pressure. 

Benzylarsine  and  Platinic  Chloride. — When  equimolecular 
weights  of  benzylarsine  and  platinic  chloride  (10  per  cent  solu- 
tion) were  brought  together  in  a sealed  tube,  a black,  oily  sub- 
stance, followed  by  a black  amorphous  mass,  was  noticed. 
After  being  washed  with  alcohol  and  ether,  the  chlorplatinate 


Reactions  of  the  Arsines.  115 

"was  dried  and  ignited ; the  odors  of  arsenic  trioxide  and  stibine 
were  given  off  during  the  heating. 

0.112 1 gram  substance  yielded  0.0423  gram  Pt. 

Calculated  for 

C7H7AsH2.PtCl4.  Found. 

Pt  38.49  38.18 

Hydriodic  Acid. — Heated  with  2 molecules  of  hydriodic  acid 
at  140°  for  one  hour,  the  benzylarsine  yielded  hydrogen,  a 
brown  black  solid, ^ and  an  oil  (evidently  benzylarsine  diiodide). 

Bromine. — With  a molecule  of  bromine  at  ordinary  tempera- 
ture, the  arsine  yielded  hydrogen,  transparent  crystals,  and  a 
heavy,  dark  oil. 

Oxygen. — Permitted  to  oxidize  in  the  air,  the  arsine  yielded 
benzylarsonic  acid  (melting  at  167°)  and  a red  product,  which 
was  analyzed: 

0.1180  gram  substance  gave  0.1837  gram  Mg2As207. 

Calculated  for 

(C7H7As)4.  Found. 

As  76.72  75.33 

T ripropylarsine. 

When  103  grams  of  ti-propyl  chloride,  120  grams  of  arsenic 
trichloride,  and  75  grams  of  sodium  were  brought  together  in  a 
flask  attached  to  a long  reflux  condenser,  a reaction  took  place;^ 
after  standing  all  night  and  heating  gently  for  i to  2 hours  on  the 
water  bath,  the  reaction  was  found  to  be  complete.  After 
filtering  rapidly  and  distilling  off  the  ether,  60  grams  of  oil  were 
obtained ; this  was  distilled  three  times  at  ordinary  pressure  and 
the  following  fractions  were  obtained : 

1.  ioo°-i40°  2 grams  4.  205°-220°  10  grams 

2.  I40°-200°  8 “ 5.  220°-270°  4 “ 

3.  200°-205°  18  “ 

The  lower  fractions  showed  the  presence  of  2 to  3 per  cent  of 
chlorine;  evidently  primary  and  secondary  arsine  chlorides 
were  present;  on  standing  exposed  to  the  air,  a white  solid 
formed  and  the  oil  separated  into  two  layers ; the  solid  gave,  on 

1 See  page  120. 

* Cf.  This  Journal,  35,  42. 


Ii6 


Dehn, 


analysis,  4 per  cent  of  chlorine;  evidently  the  compound  (CgHy)^ 
AsO.(C3H7)2AsOC1  was  formed. 

The  fractions  below  210°  were  boiled  with  an  excess  of  bromine 
water;  after  concentrating,  the  heavy,  red  oil  (25  grams)  was 
washed  with  water,  dried,  and  analyzed  for  bromine  (21.42  per 
cent  Br,  calculated  for  (C3H7)3AsBr2  = 43.90  per  cent).  To  re- 
move the  primary  and  secondary  arsine  derivatives  which 
evidently  were  present,  the  oil  was  heated  with  aqueous  am- 
monia and  the  residual  oil  was  removed,  reduced  by  means  of 
zinc  and  hydrochloric  acid,  extracted  with  ether,  and  distilled 
under  reduced  pressure.  It  boiled  at  167°  (90  mm.)  and  158° 
(73  mm.). 

0.1312  gram  substance  gave  0.2550  gram  CO2  and  0.1183 
gram  H2O. 

Calculated  for 

(C3H7)3As.  Found. 

C 52-94  53-02 

H 9.95  10.02  ■ 

A molecular  weight  determination  by  the  Dehn  method^  was 
made:  0.2242  gram  substance  gave  12.99  cc.  of  vapor  at  1564 
mm.  and  above  251  °.  Vapor  pressures:  92 ° — 16 1 mm. ; 143° — 
283  mm.;  195° — 482  mm.;  212° — 844  mm.;  251° — 1564  mm. 

Calculated  for 

(C8H7)sAs.  Found. 

Mol.  Wt.  202  204 

Oxygen. — When  tripropylarsine  was  brought  into  contact 
with  air  contained  in  the  Dehn  hygrometer,^  no  change  in 
volume  was  observed;  when  a little  concentrated  sulphuric 
acid  was  then  admitted,  rapid  oxidation  resulted,  as  was  shown 
by  the  rapid  decrease  of  the  air  volume. 

Decomposition  of  Arsenic  Derivatives  by  Heat.^ 

Isoamylarsonic  Acid.* — When  7.2  grams  of  the  pure  acid  were 
heated  in  a sealed  tube  filled  with  carbon  dioxide,  no  reaction 
was  noticeable  even  after  heating  for  15  hours  at  180°  (the  acid 

1 J.  Am.  Chem.  Soc.,  29,  1063. 

^ Ibid.,  29,  1053. 

2 Cf.  J.  Am.  Chem.  Soc.,  28,  355-59;  This  JoxmKAL,  36,  8. 

* J.  Am.  Chem.  Soc.,  28,  353. 


Reactions  of  the  Arsines. 


117 


melts  at  194°).  After  heating  for  three  hours  at  240°,  a slight 
darkening  and  a partial  yield  of  a liquid  were  observed;  after 
heating  for  four  hours  at  285°,  the  formation  of  the  liquid  and  a 
mass  of  pearly  crystals  was  complete.  On  opening  the  tube, 
no  pressure  was  observed;  on  distilling  the  liquid  contents,  a 
large  yield  of  isoamyl  alcohol  and  some  isoamyl  oxide  was  ob- 
tained. Since  the  flat,  pearly  crystals  did  not  melt  at  300°, 
did  not  suffer  a loss  in  weight  on  subliming,  and  when  dissolved 
in  hydrochloric  acid  yielded  with  hydrogen  sulphide  a yellow 
precipitate,  they  were  identified  as  arsenic  trioxide.  Therefore 
the  above  decomposition  was  as  follows : 

2C5H11ASO3H2  = 2C5H11OH  + AS2O3  + H2O. 

Phenylarsonic  Acid} — This  acid  did  not  decompose  on  heating 
for  three  hours  at  285°  (melting  point,  158°);  after  heating 
for  twenty-four  hours  at  320°  it  was  changed  to  two  liquid 
layers  and  a white  solid  (arsenic  trioxide).  The  upper,  dark 
colored  liquid  layer  was  separated  from  the  lower  layer  (water) 
and  identified  as  phenyl  oxide  (boiling  point,  252°),  therefore 
we  have  the  following  reaction: 

2CeH5As03H2  = -b  AS2O3  + 2H2O. 

Monophenylarsine} — When  this  compound  was  sealed  in  a 
tube  with  carbon  dioxide  and  heated  for  two  hours  at  180°,  no 
change  was  observed  on  cooling;  after  heating  for  three  hours 
at  240°,  a red  brown  solid  and  a light  green  oil  were  found; 
after  heating  for  three  hours  more  at  310°,  a black  residue 
coating  the  inner  surfaces  of  the  tube  was  observed.  The  excess 
of  gas  found  in  the  tube  proved  to  be  hydrogen;  an  ether  ex- 
tract of  the  residue  yielded  well-defined  crystals  of  triphenyl- 
arsine;  the  black  residue  contained  95.1  per  cent  of  arsenic. 
Therefore  the  reaction  is  expressed  by  the  following  equation: 

3C6H5ASH2  = (C6H5)3As  -b  2As  -b  3H2. 

Monomethylarsine.^ — This  primary  arsine  was  heated  for 
three  hours  at  240°  without  effect;  after  heating  for  three 

1 Ann.  Chem.  (Liebig),  208,  34;  This  Journal,  33,  132. 

* This  Journal,  33,  147. 

3 Ber.  d.  chem.  Ges.,  34,  3597.  This  Journal,  33,  120. 


Ii8 


Dehn, 


hours  at  310°  it  yielded  a black,  metallic  mirror.  The  excess  of 
gas  formed  was  washed  successively  with  solutions  of  sodium 
hydroxide,  silver  nitrate,  and  bromine;  the  residual  gas,  which 
burned  with  a blue  flame,  was  proved  by  the  explosion  method 
to  be  a mixture  of  methane  and  hydrogen.  At  least  one  phase 
of  the  decomposition  is  expressed  by  the  equation 

2CH3ASH2  = 2CH4  + 2As  + H2. 

Monoethylarsine.^ — When  this  arsine  was  heated  for  three 
hours  at  210°,  only  a slight  blackening  was  noticed;  after  three 
hours  at  235°,  the  black  metallic  deposit  on  the  walls  of  the 
tube  was  complete.  The  excess  of  gas  in  the  tube  was  washed 
as  described  above.  On  exploding  0.9  of  the  residual  gas  in 
the  presence  of  an  excess  of  oxygen,  it  suffered  a loss  of  1 1.3  cc. ; 
with  potassium  hydroxide  a further  loss  of  8.4  cc.  resulted. 
The  black  deposit  (0.1036  gram)  yielded  95.17  per  cent  of 
arsenic  (0.1990  gram  Mg2As207).  An  alcohol-ether  extract 
of  the  original  contents  of  the  tube  yielded  some  triethylarsine. 
Therefore  the  following  reactions  are  involved: 

2C2H5ASH2  = 2C2He  4-  2As  + H2, 

3C2H6ASH2  * (C2H5)3As  -f  2As  -t-  3H2. 

Dtisoamylarsine.^ — Heating  for  two  hours  at  220°  yielded  a 
little  red  solid;  heating  for  three  hours  at  240°  to  260°  gave  a 
black,  metallic  deposit.  When  65  cc.  of  the  excess  gas  were 
freed  from  carbon  dioxide  (22.2  cc.)  and  then  was  treated  with 
bromine  water,  a contraction  of  2.0  cc.  resulted;  the  residual 
gas  burned  with  a luminous  flame.  The  liquid  contents  of  the 
tube,  after  extracting  with  alcohol  and  ether,  yielded  at  about 
175°  a liquid  burning  without  depositing  arsenic  (decane)  and 
at  about  240°  a liquid  which,  by  its  odor,  by  its  decomposition 
on  heating,  and  by  its  reaction  with  bromine,  was  proved  to  be 
triisoamylarsine.  The  black  solid  (0.1407  gram)  gave  on  one 
analysis  86.48  per  cent  of  arsenic  (0.2466  gram  Mg2As207). 
The  consecutive  reactions  probably  are  as  follows : 

6(C5HJ2AsH  = 4(C5HJ3As  -h  2As  4-  3H2, 

2(C5Hii)2AsH  = CsHjq  -\r  C5HJ2  4"  Cjo  H22  4"  2 As. 

1 This  Journal,  SS,  143. 

2 Ibid.,  S6.  53. 


Reactions  of  the  Arsines, 


119 

Diphenylarsine} — Heating  for  two  hours  at  245°  produced 
only  a little  blackening;  heating  for  three  hours  at  295°  effected 
decomposition.  The  residual  excess  gas  proved  to  be  hydro- 
gen; the  alcohol-ether  extract  of  the  residue  yielded  a white, 
crystalline  product,  which  (0.0852  gram)  yielded  on  analysis 
25.15  per  cent  of  arsenic  (0.0443  gram  Mg2As207) — evidently 
it  was  triphenylarsine  (calculated.  As  = 24.51  per  cent).  Two 
analyses  of  the  black  residue  (77.46  per  cent  As  and  77.70  per 
cent  As)  showed  here,  as  in  other  cases  of  its  production,  that 
it  is  probably  mixed  with  the  tertiary  arsine.  The  reactions 
are  expressed  by  the  following  equations: 

6(C6H5)2AsH  = 4(C6H5)3As  + 2As  -H  3H2, 

2(CeH5)3As  = 3C12H10  + 2 As. 

Tripropylarsine} — No  evidence  of  decomposition  was  notice- 
able below  287°;  after  heating  for  two  hours  at  295°,  a yellow 
liquid  was  observed.  On  opening  the  tube  considerable  pres- 
sure was  noticed;  44  cc.  of  this  gas,  after  washing  successively 
with  caustic  soda  and  bromine  water,  gave  16  cc.  of  gas  which 
by  shaking  with  alcohol  lost  8.5  cc.  The  gas  which  was  sol- 
uble in  alcohol  burned  with  a blue  flame.  The  residual  liquid 
in  the  tube  had  a cacodyllike  odor.  The  probable  partial 
reaction  was 

4(C3H7)3As  = (C3H7AS),  -h  4CeH,,. 

Triethylarsine. — Heated  at  190°  to  215°  for  three  hours,  it 
darkened;  at  245°  for  two  hours,  a yellow  oil  and  some  solid 
were  formed;  at  265°  for  three  hours,  considerable  excess  gas, 
a greenish  yellow  to  gray  black  residue  and  only  a little  liquid 
were  observed.  The  solid  gave,  on  analysis,  44.09  per  cent 
arsenic  (o.  1264  gram  gave  o.  1 129  gram  Mg2As207) ; calculated  for 
(C2H5)3As  = 46.29.  The  alcohol-ether  extract  of  the  solid 
yielded  an  oil  which  by  its  odor  and  reaction  with  bromine  was 
shown  to  be  unchanged  triethylarsine.  The  probable  partial 
reaction  was 

4(C2H5)3As  = (C3H3AS),  + 4C.H,„. 

* This  Journal,  36,  45. 

* See  page  115. 


120 


Dehn. 


Benzylarsine} — When  0.5  gram  of  benzylarsine,  in  a sealed 
tube  from  which  the  air  had  been  exhausted,  was  heated  for 
two  hours  at  250°,  a reaction  resulted.  A little  gas,  a little  oil,  ' 
and  a glistening,  black  solid  were  formed.  The  black  solid  was 
washed  and  analyzed; 0.1473  gram  gave  0.1370  gram  Mg2As207, 
which  is  equivalent  to  45.00  per  cent  of  arsenic — calculated  for 
(C6H5CH2As)4  is  45.18  per  cent.  Therefore  the  following  re- 
- action  probably  takes  place : 

4CeH5CH2AsH2  ->  (CeH5CH2As)4  + 4H2. 

Cacodyl? — When  5.3  grams  of  crude  cacodyl  (cacodylic 
oxide)  were  heated  for  two  hours  at  340°  in  a sealed  tube  filled 
with  carbon  dioxide,  a black,  metallic  deposit  and  a mobile, 
yellow  oil  were  formed;  on  opening  the  tube  considerable  pres- 
sure was  observed.  After  washing  with  a solution  of  potash, 
the  residual  gas  (about  25  per  cent)  was  found  to  burn  with  an 
arsenic  flame  and  to  dissolve  in  a solution  of  silver  nitrate;  its 
odor  and  other  properties  characterized  it  as  trimethylarsine.^ 
After  freeing  it  from  the  oil  and  washing  it  with  alcohol  and 
ether,  0.1446  gram  of  the  black  residue  yielded  0.2500  gram 
Mg2As207  or  83.65  per  cent  As;  calculated  for  (CH3As)4  is  83.33 
per  cent  As.  The  oil  distilled  mostly  below  80°  (trimethylarsine 
boils  at  70°).^  The  decomposition  of  cacodyl  at  high  tempera- 
tures is  represented  by  the  following  equation: 

4(CH3)2AsAs(CH3)2  4(CH3)3  As  + (CH3As)4. 

That  the  oil  was  trimethylarsine  was  confirmed  by  the  fol- 
lowing experiments.  Treated  with  an  excess  of  an  aqueous 
solution  of  mercuric  chloride,  a voluminous  white  precipitate 
was  formed;  by  recrystallization  from  hot  water,  pearly  white 
leaflets  were  obtained.  0.7070  gram  substance  gave  0.3918 
gram  AgCl. 

Calculated  for 

[(CH3)3As]2HgCl2.  Found, 

Cl  13.86  13.68 

Trimethylar sine-mercuric  chloride  was  formed. 

^ See  page  113. 

2 Ann.  Chem.  (Liebig),  107,  261.  This  Journal,  36,  2. 

» Ann.  Chem.  (Liebig),  92,  361;  112,  228. 

* Jahres.  d.  Chem.,  1865,  538. 


Reactions  of  the  Arsines, 


I2I 


A chloroform  solution  of  trimethylarsine,  treated  with  a 
chloroform  solution  of  bromine,  evolved  much  heat  and  pre- 
cipitated a heavy,  red  oil  that  soon  solidified  to  coarse,  red 
orange,  prismatic  crystals.  The  substance  was  rapidly  de- 
composed by  atmospheric  moisture  and  melted  at  94°. 

0.7088  gram  substance  gave  0.9481  gram  AgBr. 

Calculated  for 

(CH3)3AsBr2.  Found. 

Br  57.14  56.92 

Trimethylarsine  dibromide  was  formed. 

III.  Reactions  of  Dimethylarsine.^ 

With  Burtox  B.  Wilcox. 

Isoamylene. — When  equimolecular  quantities  of  dimethyl- 
arsine  and  isoamylene  were  heated  for  one  hour  at  120°,  no 
change  was  noticeable.  Evidently  a reaction  indicated  in  the 
equation 

(CH3)2AsH  -h  CsH.o  = (CH3)2(C5H,,)As 

does  not  take  place.^The  vapor  pressures  of  amylene,  methyl- 
arsine  dichloride,  and  a mixture  of  the  two  in  equal  volumes 
were  determined;  these  and  other  data  are  given  below: 


Temperature.  Isoamylene. 

CH3ASCI2. 

Mixture. 

Vapor  pressure 
depression.* 

26.5  531.7 

9.0 

262.4 

260.3 

Amyl  chloride. 

28.5  64.3 

AsCls. 

II  .0 

54-9 

20.6 

Propyl  iodide. 

28.5  50.1 

AsClj. 

II  .0 

24.1 

37-0 

Benzyl  Chloride. — Equimolecular  quantities  of  dimethyl- 
arsine  and  benzyl  chloride  in  ether  solution  in  a sealed  tube 

1 Secondary  Arsines.  Dehn  and  Wilcox:  This  Jothinal,  35,  1-54. 

* If  the  depression  of  vapor  pressures  of  liquid  mixtures  is  an  indication  of  molec- 
ular coalescence,  then  the  products 

(CH,)2AsH  CI3AS  CI3AS 

CH2='CH— CsHy’  ci—CgHn’  i— C3H7* 

are  probably  formed,  though  the  molecularly  rearranged  products 

(CH3)2As— CH2— CH?— C3H7,  CbAs— CsHu,  CblAs— C3H7, 


are  not  formed. 


122 


Dehn, 


showed  no  evidence  of  reaction,  after  standing  for  two  months. 

Phosphoric  Acid. — Equimolecular  quantities  of  dimethyl- 
arsine  and  metaphosphoric  acid  in  a sealed  tube  showed  no 
evidence  of  reaction,  even  after  heating  for  two  hours  at  95°. 

Phenylarsine  Dichloride. — When  2.06  grams  of  dimethyl- 
arsine  (2  mols.)  and  4.3  grams  of  phenylarsine  dichloride 
(i  mol.)  were  brought  together  in  a sealed  tube  filled  with  car- 
bon dioxide,  a dark,  red  brown  solid  and  jine,  glistening  crystals 
were  formed.  Little  pressure  was  observed  on  opening  the 
tube  (absence  of  hydrogen  or  hydrochloric  acid  gas) ; an  ether 
extract  of  the  contents  of  the  tube,  on  being  filtered  and  con- 
centrated in  a vacuum  desiccator,  yielded  beautiful,  white, 
compact  crystals,  which  were  immediately  decomposed  by 
atmospheric  moisture.  After  washing  with  a little  carbon 
disulphide,  the  crystals  were  dried  and  quickly  analyzed  for 
chlorine.  0.3683  gram  of  substance  gave  0.3058  gram  of 
AgCl. 

Calculated  for 

(C6H5AsCl2)(CH3)2AsH.  Found. 

Cl  21.59  20.57 

Dimethylarsinephenylarsine  dichloride  decomposes  rapidly 
when  exposed  to  the  air,  precipitating  from  an  ether  solution 
an  oil,  which  was  analyzed.  0.2514  gram  substance  gave 
0.1641  gram  AgCl. 

Calculated  for 

CeHsAsCl — As(CH3)j.  Found. 

Cl  12.00  16.62 

The  oil  was  evidently  a mixture.  The  initial  reaction  of 
phenylarsine  dichloride  and  dimethylarsine  may  be  expressed 
(CH3)2AsH 
thus:  11 

C,H  — AsCl, 

Diisoamylarsine  Chloride.^ — When  equimolecular  quantities 
of  dimethylarsine  and  diisoamylarsine  chloride  were  brought 
together  in  a sealed  tube  filled  with  carbon  dioxide,  no  change 
was  apparent  to  the  eye,  even  after  heating  for  five  hours  at 
100°.  On  opening  the  tube  no  pressure  (absence  of  dimethyl- 
arsine) was  observed;  after  treating  with  water,  the  oil  fumed, 

1 Cf.  This  Journal,  36,  31. 


Reactions  ^of  the  Arsines, 


123 


possessed  the  odor  of  amylarsine,  and  undoubtedly  was  df- 
isoamyldimethylcacodyl.  The  reaction  evidently  was  as  follows : 

(CH,),AsH  (CH3)2As 

II  ->  I +HC1. 

(C3H„)2AsC1  (C,H,0,As 

Propyl  Iodide. — When  1.84  grams  of  dimethylarsine  (i  mol.) 
and  5.83  grams  of  propyl  iodide  (2  mols.)  were  brought  together 
in  a sealed  tube  filled  with  carbon  dioxide  and  the  mixture 
was  allowed  to  stand  for  a number  of  days,  a slightly  colored 
oil  and  some  white  crystals  were  formed.  On  opening  the  tube, 
pressure  was  observed;  the  crystals,  easily  decomposed  by 
atmospheric  moisture  and  forming  an  oil  of  a tertiary  arsine 
odor,  were  nearly  insoluble  in  chloroform  (all  tetralkylarsonium 
iodides  are  easily  soluble  in  chloroform).  After  washing  with 
chloroform  they  were  analyzed  with  the  following  results: 
0.9038  gram  substance  gave  0.7651  gram  Agl. 

Calculated  for 

(CH3)2(C3H7)AsHI.  Found. 

I 46.01  45.75 

Some  of  this  dimethyl-n-propylarsonium  iodide  was  treated 
with  an  excess  of  isoamyl  iodide  and  heated  in  a sealed  tube  for 
two  hours  at  120°.  The  dimethyl-n-propylisoamylarsonium 
iodide  was  separated  by  the  usual  method : 

0.6805  gram  substance  gave  0.4663  gram  Agl. 

Calculated  for 

(CH3)2(C3H7)(C5Hn)AsI.  Found. 

I 36.70  37.03 

Diisoamylarsine  and  n-Propyl  Iodide.  When  2.5  grams  of 
diisoamylarsine  (i  mol.)  and  2.8  grams  of  n-propyl  iodide  (2 
mols.)  were  heated  for  two  hours  at  160°  in  a sealed  tube  filled 
with  carbon  dioxide,  a dark  red  liquid  was  obtained.  On 
opening  the  tube,  considerable  gas  was  given  off ; after  washing 
with  caustic  potash,  alcohol,  and  water,  the  residual  gas  gave 
an  excellent  test  for  hydrogen.  The  product,  diisoamyldi-n- 
propylarsonium  iodide,  was  separated  in  the  usual  manner  and 
analyzed  with  the  following  results:  0.6909  gram  substance 
gave  0.3761  gram  Agl. 

Calculated  for 

(C6H„)2(C3H7)2AsI.  Found. 

29.53  29.42 


I 


124 


Dehn, 


Cacodyl  and  Propyl  Iodide. — When  4.1  grams  of  crude 
cacodyl  (i  mol.)  and  12.5  grams  of  n-propyl  iodide  (4  mols.) 
were  heated  for  2 hours  at  140°  in  a sealed  tube  filled  with 
carbon  dioxide,  a red  oil  was  obtained.  After  heating  with  a 
concentrated  solution  of  potash,  filtering,  dissolving  in  chloro- 
form, and  reprecipitating  with  ether,  the  substance  was  obtained 
as  yellow  crystals.  The  process  of  purification  was  repeated 
2 or  3 times  but  a colorless  product  could  not  be  separated; 
after  dissolving  in  a little  water,  filtering,  and  evaporating  to 
dryness,  light  yellow  crystals  were  obtained.  0.6882  gram 
substance  gave  0.4980  gram  Agl. 

Calculated  for 

(CH3)2(C8H7)aAsI.  Found. 

I 39-93  39-11 

When  dimethyldi-n-propylarsonium  iodide  was  treated  with  an 
excess  of  mercuric  chloride,  a white  precipitate  was  formed; 
after  crystallizing  from  hot  water,  white  leaflets  were  obtained ; 
0.2960  gram  substance  gave  0.2556  gram  AgI.2AgCl. 

Calculated  for 

(CH3)j(C3H7)2AsIHgCl2.  Found. 

I.2CI  33.59  32.74 

Acetyl  Iodide  and  Dimethylarsine. — When  equimolecular 
quantities  of  acetyl  iodide  and  dimethylarsine  were  brought 
together  in  ether  in  a sealed  tube,  an  immediate  precipitation 
of  a yellow  solid  and  the  liberation  of  considerable  heat  were 
observed.  After  some  time  the  solid  changed  to  a yellow  oil 
and  clusters  of  needlelike  crystals.  After  two  years,  the  tube 
was  opened;  the  ether  solution  was  treated  with  an  aqueous 
solution  of  mercuric  chloride,  when  a voluminous  white  precipi- 
tate was  formed.  After  washing  with  water,  alcohol,  and  ether 
the  substance  was  analyzed.  0.3803  gram  substance  gave 
0.2756  gram  silver  halide. 

Calculated  for 

(CH3)2AsHiO.HgICl.  Found. 

Cl.I  33.51  31.10 

The  residue  in  the  tube  was  washed  repeatedly  with  ether 
and  was  then  dissolved  in  water  and  boiled  with  a solution  of 
mercuric  chloride.  The  odor  of  acetaldehyde  was  observed, 


Reactions  of  the  Arsines. 


125 


while  the  oil,  which  was  first  formed,  was  slowly  changed  to 
mercurous  iodide  and  the  double  compound  with  mercuric 
chloride.  The  reactions  evidently  can  be  represented  as  fol- 
lows : 


(CH3),AsH 


H 

I 

(CH3),As-I 


(CH3)3AsI  + CH3CHO. 


CH3CO— I 


CHgC^O 


Chlorcarbonic  Ethyl  Ester  and  Dimethylarsine.  When  equi- 
molecular  quantities  of  the  two  substances  were  brought  to- 
gether in  a sealed  tube  filled  with  carbon  dioxide,  no  reaction 
was  evident  to  the  eye;  however,  on  opening  the  tube,  great 
pressure  (ethyl  formic  ester  boils  at  54.4°)  and  combustible 
vapors  were  observed;  the  residual  oil  possessed  the  odor  of 
cacodyl  chloride,  therefore  a reaction  had  resulted,  as  follows: 

(CH3)2AsH  + CICOOC2H5  ->  (CH3)2AsC1  + HCOOC2H5. 


The  oil  was  further  identified  as  cacodyl  chloride  by  shaking 
its  ether  solution  with  an  aqueous  solution  of  mercuric  chloride 
— a voluminous  white  precipitate  resulted.  The  substance 
was  recrystallized  from  hot  water.  0.5451  gram  substance 
yielded  0.3970  gram  AgCl. 

Calculated  for 

(CH3)2AsH20.HgCl2i.  Found. 

Cl  17-98  * 18.07 


Sulphur  Bichloride.^  When  2.13  grams  of  dimethylarsine 
(2  mols.)  and  2.06  grams  of  sulphur  dichloride  (i  mol.)  were 
brought  together  in  a sealed  tube  containing  carbon  dioxide, 
a very  violent  reaction  (much  heat)  resulted.  After  standing 
for  two  years,  a slightly  yellow  oil,  a yellow  amorphous  solid 
(sulphur),  and  transparent  tablets  and  needles  were  observed. 
On  opening  the  tube  a considerable  pressure  of  methyl  sulphide 
(identified  by  its  odor  and  by  the  blackening  of  lead  acetate 
paper)  was  observed.  By  heating  the  tube  on  the  water  bath, 
the  liquid  distilled  out  and  the  crystals  increased  in  quantity 
(they  did  not  melt  at  100°).  When  treated  with  ether  (evi- 

» Cf.  page  127, 

2 Cf.  This  Journal,  35,  38. 


126 


Dehn, 


dently  containing  a little  water)  the  crystals  were  decomposed, 
thereby  giving  rise  to  the  odor  of  cacodyl  chloride  and  precipi- 
tating finely  divided  sulphur.  A chloroform  solution  of  the 
crystals  standing  in  a desiccator  deposited  sulphur.  These 
crystals  were  not  analyzed ; that  they  are  an  intermediate  prod- 
uct in  the  following  reaction  is  sufficiently  evident: 

2(CH3)2AsH  -f-  SCI2  2(CH3)2AsC1  -}-  S. 

Arsenic  Trioxide. — When  1.7  grams  of  dimethylarsine  (3 
mols.)  and  2.1  grams  of  arsenic  trioxide  (2  mols.)  were  brought 
together  in  a sealed  tube  filled  with  carbon  dioxide,  a very  slow 
reaction  ensued — a dark  brown  solid  gradually  replaced  the 
trioxide.  The  tube  was  heated  for  five  hours  at  100°  and  then 
was  permitted  to  stand  for  two  years;  on  opening  the  tube 
some  unchanged  arsine  but  no  arsenic  trioxide  was  observed. 
The  red  brown  solid  was  analyzed. 

0.1246  gram  substance  gave  0.2137  gram  Mg2As207. 

0.1046  gram  substance  gave  0.1790  gram  Mg2As207. 

Calculated  for  Pound. 

AsjOafCHsAs)!.  (CH3As)4.  I.  II. 

As  75.75  83.33  ■ 82.99  82.80 

Evidently  the  reaction  is  largely  as  follows: 

2(CH3)2AsH  + AS2O3  = (CH3As)4  + H2O  02- 

Arsenic  Trichloride.^ — When  3 grams  of  dimethylarsine 
(2  mols.)  and  2.56  grams  of  arsenic  trichloride  (i  mol.)  were 
brought  together  in  ether  in  a sealed  tube,  a dark  brown  solid 
was  precipitated  at  once.  After  standing  for  two  years  the 
ether  solution  was  poured  out;  the  amorphous  brown  solid 
was  seen  to  be  mixed  with  /ong,  prismatic,  transparent  crystals, 
which  were  decomposed  rapidly  by  contact  with  the  atmosphere, 
hence  they  were  not  separated  and  analyzed.  Evidently  they 
were  an  intermediate  compound.  The  red  brown  substance 
was  washed  with  dilute  hydrochloric  acid  and  analyzed : 

0.2453  gram  substance  gave  0.4238  gram  Mg2As207. 

Calculated  for 

(CH3As)4.  Found. 

As  83.33  83.60 


1 Cf.  This  Journal,  35,  40. 


Reactions  of  the  Arsines. 


127 


The  ether  solution  was  treated  with  an  aqueous  solution 
of  mercuric  chloride;  the  voluminous  white  precipitate  was 
recrystallized  from  hot  water  and  analyzed. 

0.6630  gram  substance  gave  0.4800  gram  AgCl. 

Calculated  for 

(CH3)2AsH20HgCV.  Found. 

Cl  1798  17-87 

Evidently  the  end  reaction  is  as  follows: 

4(CH3)2AsH  + 2ASCI3  = (CH3As)4  + 2(CH3)2AsC1  + 4HCI 

Urbana,  Illinois, 

August  5,  1907. 


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